HONOLULU (Reuters) - United States President Barack Obama called Philadelphia Police Commissioner Charles Ramsey on Sunday to express his outrage over the recent killings of two New York City Police officers, White House spokesman Eric Schultz said.

Mr Obama recently named Mr Ramsey co-chair of a task force to examine policing practices across the United States following a Missouri grand jury's decision not to indict a white police officer in Ferguson, Missouri for killing an unarmed black teenager.

The call came one day after an attack by 28-year-old Ismaaiyl Brinsley, who allegedly walked up to two officers in a parked squad car in Brooklyn and shot them dead.

In the call, Mr Obama asked Mr Ramsey to use his task force to further his message that such acts against the police are to be condemned.